Heat exchanger assembly for an aircraft control

ABSTRACT

A heat exchanger assembly for an aircraft control has an aircraft control for controlling an operation of an aircraft. The aircraft control is in thermal communication with a first fluid. A first thermoelectric device is configured to transfer heat between the first fluid and the second fluid against a temperature gradient of the first fluid and the second fluid. A temperature sensor is provided for sensing a temperature of the first fluid. A temperature control is also configured to control the first thermoelectric device based on an input from the temperature sensor.

BACKGROUND OF THE INVENTION

This invention relates to a heat exchanger for an aircraft control. Anaircraft has a number of electronic controls used to control anoperation of the aircraft. One such control manages the function of theaircraft engines and is commonly known as a Full Authority DigitalEngine Control or FADEC. The FADEC is generally installed in anenvironment of the aircraft susceptible to both very high temperaturesand very low temperatures. For example, the FADEC may be installed inthe engine bay where large amounts of heat are generated during flightconditions. In these conditions, the FADEC requires a substantial amountof cooling to limit its operating temperature. When the aircraft is notin flight, however, the engine bay may be extremely cold when ambientair temperature is low. At these conditions, the FADEC requires verylittle, if any, cooling.

The FADEC, like many aircraft controls, is composed of electroniccomponents that require moderate and uniform temperatures for optimaloperation. The large temperature swings experienced by the FADEC is notconducive to the best performance of these temperature sensitivecomponents. While there are electronic components that are capable ofperforming at the extreme temperature conditions of the aircraft, thesecomponents are generally very expensive and have relatively lowperformance (memory, process, or speed) compared to most modernelectronics.

A need therefore exists for an assembly and technique that maintains theelectronics of an aircraft control within their designed operatingtemperatures.

SUMMARY OF THE INVENTION

A heat exchanger assembly includes an aircraft control. The aircraftcontrol is in thermal communication with a first fluid. A firstthermoelectric device is configured to transfer heat between the firstfluid and a second fluid against a temperature gradient of the firstfluid and the second fluid. A temperature sensor is provided for sensinga temperature of the first fluid. A temperature control is alsoconfigured to control the first thermoelectric device based on an inputfrom the temperature sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of this invention will becomeapparent to those skilled in the art from the following detaileddescription of the currently preferred embodiment. The drawings thataccompany the detailed description can be briefly described as follows:

FIG. 1 illustrates a schematic view of a heat exchanger assembly for anaircraft control, showing first thermoelectric device, secondthermoelectric device and third thermoelectric device.

FIG. 2 illustrates a perspective view of the thermoelectric devices ofFIG. 1, including a plurality of flow conduits.

FIG. 3 illustrates a close up view of the thermoelectric device of FIG.2, highlighting the flow conduits in relation to a thermoelectricdevice.

FIG. 4 illustrates an alternative arrangement of flow conduits of FIG.3.

FIG. 5 illustrates an exploded view of the thermoelectric device of FIG.3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1 there is shown heat exchanger assembly 10 for aircraft control14. FIG. 1 is a schematic and shows the general operation of heatexchanger assembly 10. As shown, aircraft control 14, such as a FADEC,for example, is composed of printed circuit boards 12. Printed circuitboards 12 are mounted to frame 19 in a tiered fashion. Printed circuitboards 12 are mounted to heat sinks 15 and conduction posts 17, whichare all mounted to frame 19. This arrangement permits heat to betransferred between printed circuit boards 12 and frame 19.

Frame 19 has first fluid 18 to act as a heat exchanger for printedcircuit boards 12 through heat sinks 15 and heat conduction posts 17. Inthis regard, first fluid 18 may be any of a variety of fluids, includingaircraft engine fuel, ethylene glycol or any antifreeze. Frame 19 hasfluid channel 21, an internal conduit that allows the circulation offirst fluid 18 via pump 115 to thermoelectric assembly 108 and back toframe 19. First fluid 18 is contained in a closed fluid loop, hereclosed first loop 102.

At thermoelectric assembly 108, first fluid 18 exchanges heat withsecond fluid 34. Second fluid 34 is contained in another closed loop,second closed loop 103, which includes, by way of example, aircraft fuelreservoir 36, pump 117, and thermoelectric assembly 108. Pump 117 pumpssecond fluid 34, here aircraft engine fuel, through thermoelectricassembly 108 back to fuel reservoir 36.

The exchange of heat between first fluid 18 and second fluid 34 occursthrough thermoelectric assembly 108. Normally, second fluid 34 is at ahigher temperature than first fluid 18. Hence, transferring heat fromfirst fluid 18, which is at a lower temperature than second fluid 34, isagainst the temperature gradient between the two fluids and generallywould not occur. Thermoelectric assembly 108 is provided to therebyallow first fluid 18 to transfer heat to second fluid 34 against thetemperature gradient of the two fluids.

Thermoelectric assembly 108 has first thermoelectric device 22, secondthermoelectric device 70 and third thermoelectric device 82. As shown inFIG. 5, each thermoelectric device, such as first thermoelectric device22, has thermoelectric elements 111 disposed on substrate 24. Eachthermoelectric element 111 is configured to pump heat as known against atemperature gradient. Thermoelectric elements 111 are collectivelyoriented so that heat may be pumped either in the direction of arrow Ror the direction of arrow S, both directions perpendicular to themounting substrate 24. The direction can be controlled by controllingthe direction of electric current flow for thermoelectric elements 111.Electric current flow in one direction will pump heat in the directionof arrow R while current flow in the opposite direction will pump heatin the direction of arrow S. Adjusting the level of electric currentwill adjust the rate of heat pumping.

First thermally conductive plate 94 and second thermally conductiveplate 98, here made of aluminum, sandwich and encase substrate 24 so asto prevent fluid from damaging thermoelectric elements 111. Becausefirst thermally conductive plate 94 and second thermally conductiveplate 98 are both made of metal, they further provide a highly thermallyconductive surface for the transmission of heat in the direction ofarrow R or in the direction of arrow S. Hence, heat may be transferredbetween two fluids, such as first fluid 18 and second fluid 34, againstthe temperature gradient between the two fluids by controlling theelectric current through thermoelectric elements 111.

The operation of heat exchanger assembly 10 will now be explained withreference to FIG. 1. Excess heat from printed circuit boards 12 ispassed to heat sinks 15 though heat conduction posts 17 and to frame 19and ultimately to first fluid 18. First fluid 18 is circulated by pump115 to thermoelectric assembly 108 along first flow path 106. There,first fluid 18 is passed in proximity to second fluid 34, which iscirculated by pump 117 in the opposite direction as first fluid 18. Heatis transferred between first fluid 18 and second fluid 34 via firstthermoelectric device 22, second thermoelectric device 70 and thirdthermoelectric device 82. These devices allow heat to be transferredeven if the temperature of first fluid 18 is lower than the temperatureof second fluid 34 at thermoelectric assembly 108. After exitingthermoelectric assembly 108, first fluid 18 has a temperature that helpsmaintain printed circuit boards 12 at their desired operatingtemperature.

With reference to first thermoelectric device 22 shown in FIG. 1-3, theheat exchange between first fluid 18 and second fluid 34 occurs bypassing first fluid 18 in the direction of arrow A through firstplurality of flow conduits 46 along first thermoelectric device 22. Asshown, second fluid 34 is channeled through second plurality of flowconduits 50 in the direction of arrow B, an opposite direction from thedirection of flow of first fluid 18. Second plurality of flow conduits50 is disposed on the other side of first thermoelectric device 22.First fluid 18 has temperature T₁ while second fluid 34 has temperatureT₂. If temperature of T₂ is greater than temperature T₁, thermoelectricdevice 22 pumps heat from first fluid 18 to second fluid 34, eventhrough second fluid 34 has a higher temperature. In this way, heat maybe transferred from first fluid 18 to second fluid 34 so as to coolfirst fluid 18 coming from thermoelectric assembly 108 to temperatureT₃, which is then returned to frame 19 along second flow path 110 so asto provide flow for moderating the temperature of printed circuit boards12.

As shown in FIG. 1, multiple layers of thermoelectric devices are usedto improve the rate of heat exchange between first fluid 18 and secondfluid 34. By way of example, thermoelectric assembly 108 has threethermoelectric devices, here first thermoelectric device 22, secondthermoelectric device 70 and third thermoelectric device 82. Firstthermoelectric device has first side 38 and second side 42 while secondthermoelectric device 70 has third side 74 and fourth side 78 and thirdthermoelectric device 82 has fifth side 86 and sixth side 90. On firstside 38 is first plurality of flow conduits while between second side 42and third side 74 is disposed second plurality of flow conduits 50.Between fourth side 78 and fifth side 86 is disposed third plurality offlow conduits 54. Fourth plurality of flow conduits 58 is on sixth side90. This layering and structuring of flow conduits and thermoelectricdevices can be seen in perspective view in FIG. 2. There, as shown, flowconduits are stacked on thermoelectric devices. More or fewer layers ofthermoelectric devices and flow conduits may be employed.

A close up view of first plurality of flow conducts 46, firstthermoelectric device 22 and second plurality of flow conduits 50 isshown in FIG. 3. There, it is shown that the temperature gradientbetween first fluid 18 and second fluid 34 is in the direction of arrowQ. In other words, first fluid 18 is cooler than second fluid 34.Thermoelectric device 22 allows heat to flow in the opposite directionof arrow Q, here the direction of arrow R so as to transfer heat fromfirst fluid 18 to second fluid 34.

As shown FIG. 1, each thermoelectric device, here first thermoelectricdevice 22, second thermoelectric device 70 and third thermoelectricdevice 82 are controlled by temperature control 30, which is incommunication with temperature sensor 26. Temperature sensor 26 measuresthe temperature of first fluid 18 in closed loop 102 and provides aninput for temperature control 30 to adjust current flow tothermoelectric devices so as to maintain first fluid 18 at a temperaturethat will maintain printed circuit boards 12 within operationalparameters.

There may be times when the temperature of first fluid 18 is too low,such as when the aircraft is inactive and ambient temperature is cold.In such an instance, first fluid 18 may, in fact, be at a lowertemperature than second fluid 34. Then, temperature control 30 mayreverse current to first thermoelectric device 22, second thermoelectricdevice 70 and third thermoelectric device 82 so that they transfer heatin the opposite direction, from second fluid 34 to first fluid 18.Temperature of first fluid 18 can be moderated in this fashion.

In FIG. 1 and 3, to facilitate the exchange of heat, first fluid 18 ispumped in the direction of arrow A while second fluid 34 is pumped inthe opposite direction, in the direction of arrow B. FIG. 4 shows analternative arrangement of flow conduits to create a cross-flow betweenfirst fluid 18 and second fluid 34. There, first fluid 18 is pumped inthe direction of arrow C, say through first plurality of flow conduits46, while second fluid 34 is pumped through second plurality of flowconduits 50 in the direction of arrow D, transverse to the direction ofarrow C.

The aforementioned description is exemplary rather that limiting. Manymodifications and variations of the present invention are possible inlight of the above teachings. The preferred embodiments of thisinvention have been disclosed. However, one of ordinary skill in the artwould recognize that certain modifications would come within the scopeof this invention. Hence, within the scope of the appended claims, theinvention may be practiced otherwise than as specifically described. Forthis reason the following claims should be studied to determine the truescope and content of this invention.

1. A heat exchanger assembly for an aircraft control, comprising: anaircraft control for controlling an operation of an aircraft; saidaircraft control in thermal communication with a first fluid; a firstthermoelectric device configured to transfer heat between said firstfluid and a second fluid against a temperature gradient of said firstfluid and said second fluid; a temperature sensor for sensing atemperature of said first fluid; and a temperature control configured tocontrol said first thermoelectric device based on an input from saidtemperature sensor.
 2. The assembly of claim 1 wherein said second fluidis an aircraft engine fuel.
 3. The assembly of claim 1 wherein saidfirst thermoelectric device has a first side and a second side, saidfirst fluid in thermal communication with said first side and saidsecond fluid in thermal communication with said second side.
 4. Theassembly of claim 3 including a first plurality of flow conduits and asecond plurality of flow conduits, said first plurality of flow conduitsfor guiding said first fluid across said first side of said firstthermoelectric device and said second plurality of flow conduits forguiding said second fluid across said second side of said firstthermoelectric device.
 5. The assembly of claim 4 wherein said firstfluid is configured to flow along said first side in a first directionand said second fluid is configured to flow along said second side in asecond direction, said first direction different than said seconddirection.
 6. The assembly of claim 5 wherein said first direction isgenerally opposite said second direction.
 7. The assembly of claim 5wherein said first direction is transverse to said second direction. 8.The assembly of claim 3 including a second thermoelectric device, saidsecond thermoelectric device spaced from said first thermoelectricdevice and having a third side and fourth side, said third side facingsaid second side of said first thermoelectric device, said second fluiddisposed between said second side and said third side.
 9. The assemblyof claim 8 including a third thermoelectric device having a fifth sideand a sixth side, said fifth side facing said fourth side of said secondthermoelectric device wherein said second thermoelectric device issandwiched between said first thermoelectric device and said thirdthermoelectric device.
 10. The assembly of claim 9 wherein said firstfluid is on said first side, said second fluid disposed on said secondside between said second side and said third side, said first fluid isalso disposed between said fourth side and said fifth side, and saidsecond fluid is also disposed on said sixth side.
 11. The assembly ofclaim 1 wherein said first thermoelectric device is configured to coolsaid first fluid when said second fluid has a higher temperature thansaid first fluid.
 12. The assembly of claim 1 including a firstthermally conductive plate and a second thermally conductive plate, saidfirst thermoelectric device sandwiched by said first thermallyconductive plate and said second thermally conductive plate, said firstthermally conductive plate and said second thermally conductive platesealing said first thermoelectric device against fluid.
 13. The assemblyof claim 1 wherein said first fluid is disposed in a closed loop.
 14. Aheat exchanger assembly for an aircraft control, comprising: an aircraftcontrol for an aircraft; said aircraft control in thermal communicationwith a first fluid, said first fluid configured to cool said control; afirst thermoelectric device configured to transfer heat from said firstfluid to a second fluid having a higher temperature than said firstfluid, said first thermoelectric device having a first side and a secondside; a second thermoelectric device, said second thermoelectric devicespaced from said first thermoelectric device and having a third side andfourth side, said third side facing said second side of said firstthermoelectric device; and wherein said first fluid is on said firstside, said second fluid between said second side and said third side,and said first fluid is also on said fourth side.
 15. The assembly ofclaim 14 including a first plurality of flow conduits and a secondplurality of flow conduits, said first plurality of flow conduits forguiding said first fluid across said first side of said firstthermoelectric device and said second plurality of flow conduits forguiding said second fluid across said second side of said firstthermoelectric device.
 16. The assembly of claim 14 wherein said firstfluid is configured to flow along said first side in a first directionand said second fluid is configured to flow along said second side in asecond direction, said first direction different than said seconddirection.
 17. The assembly of claim 14 wherein said first direction isgenerally opposite said second direction.
 18. The assembly of claim 14wherein said first direction is transverse to said second direction. 19.The assembly of claim 14 including a third thermoelectric device havinga fifth side and a sixth side, said fifth side facing said fourth sideof said second thermoelectric device wherein said second thermoelectricdevice is sandwiched between said first thermoelectric device and saidthird thermoelectric device wherein said first fluid is also disposedbetween said fourth side and said fifth side, and said second fluid isalso disposed on said sixth side.
 20. A method of controlling atemperature for an aircraft control, comprising the steps of: disposinga first fluid proximate a control for an aircraft, the first fluidconfigured to absorb heat from the control for the aircraft; providing afirst flow path to a thermoelectric device; disposing a second fluidproximate the thermoelectric device, the second fluid configured toabsorb heat from the first fluid through the thermoelectric device;providing a second flow path from the thermoelectric device to thecontrol; and wherein the first thermoelectric device is configured totransfer heat from the first fluid to the second fluid when the firstfluid has a higher temperature than the second fluid thereby cooling thefirst fluid.